WO2009077984A2

WO2009077984A2 - Redundancies and flows in vehicles

Info

Publication number: WO2009077984A2
Application number: PCT/IB2008/055354
Authority: WO
Inventors: Haifeng Wang; Honglin Hu; Ping Zhou
Original assignee: Nokia Corporation; Nokia Inc.
Priority date: 2007-12-18
Filing date: 2008-12-16
Publication date: 2009-06-25
Also published as: WO2009077984A3; WO2009077984A8

Abstract

A control system for a vehicle having plural control elements actuated at a single actuation point including a redundant electric actuator assembly including a control rod moveable linearly in two opposite directions mounting n electric motors, each motor having a controller and a feedback sensor for controlling linear movement of said rod, each motor contributing approximately 1/n of total control power required for adjusting one or more of said plural control elements, such that failure of any of said motors controllers or feedback sensors leaves sufficient predetermined minimum control power available for operating said control system.

Description

SYSTEM AND METHOD FOR DISTRIBUTED PAIRING OF RELAY AND SOURCE NODES IN A COMMUNICATION SYSTEM

This application claims the benefit of U.S. Provisional Application No. 61/014,541 entitled "System and Method for Distributed Pairing Scheme for Multiple Relay Nodes and Multiple Source Nodes in a Communication System," filed on December 18, 2007, which is incorporated herein by reference.

TECHNICAL FIELD The present invention is directed, in general, to communication systems and, more particularly, to a system and method for slot selection by a relay node in a communication system operating in a multi-relay node environment.

BACKGROUND

As wireless communication systems such as cellular telephone, satellite, and microwave communication systems become widely deployed and continue to attract a growing number of users, there is a pressing need to accommodate a large and variable number of communication devices transmitting a growing volume of data over wide cellular areas with fixed resources. Traditional communication system designs employing a fixed communication path (e.g., a direct radio path between transmitting and receiving communication devices) have become challenged to provide reliable communication over a reasonably wide geographical area in view of the need to limit transmitter power and bandwidth for the rapidly growing customer base and expanding levels of service.

Information communicated over a radio communication link such as the radio link between a communication device (e.g., user equipment) and a base station is susceptible to attenuation and signal distortion such as dispersion as a result of non-ideal communication conditions. Attenuation and distortion cause the signal delivered to a receiving communication device to be received erroneously, which can be determined by an error-detection process. If the distortion is significant, the informational content of the signal will not be accurately recovered at the receiving communication device. For instance, fading caused by multi-path transmission distorts information communicated over a communication channel. If the communication channel exhibits significant levels of fading or other signal-corrupting factors, the informational content may not be reliably recoverable by the receiving communication device.

A technique to improve reliability of communication between user equipment ("UE") and a base station ("BS," also referred to as a "Node-B") is to employ relay nodes ("RNs"), which may be fixed or mobile communication nodes (e.g., communication devices) that act as signaling relays for a weak or corrupted signal. A relay node forwards a message from a source node ("SN," e.g., a communication device), which is a node that needs assistance from a relay node, to a destination node ("DN," e.g., a communication device), which is the node that finally receives the message that may be weak or otherwise corrupted. In general, the aforementioned communications devices (e.g., user equipment, base station, source node, destination node, or relay node) form a "wireless node." For the purposes of an example, it is assumed that a source node employs one relay node to provide the relay function. It is further assumed, without limitation, that a time division duplex ("TDD") transmission mode is commonly used for the relaying function. For future networks, various fixed and mobile user equipment could be used in system design as "cooperative" fixed and mobile relay nodes to improve network performance. Message forwarding by a relay node would typically be used to support an unreliable wireless communication link between user equipment and a base station that may be susceptible to fading, low received signal strength, and/or interference by another transmitting communication device. Such "cooperative" relaying would be performed, without limitation, by mobile user equipment recognizing that other mobile and fixed user equipment would cooperate at another time to improve their communication reliability. Relay techniques have been intensively studied for use with Third Generation/Beyond

3G/Fourth Generation ("3G/B3G/4G") communication networks. By employing advanced relaying techniques in fixed and mobile relay nodes, coverage and throughput of wireless communication networks could be enhanced, as described by A. Bletsas, et αl. ("Bletsas"), in the paper entitled "A Simple Cooperative Diversity Method Based on Network Path Selection," IEEE Journal on Selected Areas in Communications, March 2006, pp. 659-672, which is incorporated herein by reference.

In a relay node-source node scenario, wherein source nodes employ relay nodes to improve communication reliability, it is preferable to properly and efficiently assign multiple relay nodes for multiple source nodes. The case needs to be avoided wherein some relay nodes are selected by more than one source node, while other cases need to be resolved wherein other source nodes have no relay nodes. It would be beneficial for a system to operate in a distributed fashion that requires less signaling overhead than a centralized arrangement in which all channel information is gathered at a central control node (e.g., at a base station).

? Several distributed multi-relay node/single source node schemes have been previously proposed, wherein one relay node is selected among multiple relay nodes for a single source node. For example, in Bletsas, cited above, the authors propose to set a timer at each relay node. Once the relay nodes hear the relaying request from the source node, the relay nodes trigger their respective timer. The expiration of each timer depends on channel qualities between the source node-relay node and the relay node-destination node. The timers are set so that the timer of the most suitable relay node expires first, and then the relay node broadcasts a "hello" signal to the rest of the relay nodes and to the single source node. Thus, the most suitable relay node is selected for a single source node. Considering the limitation as described above, however, a system and method to permit candidate relay nodes that operate in a distributed fashion to select time slots with reduced likelihood of signal collisions is not presently available for the wireless applications that lie ahead. Accordingly, what is needed in the art is a communication system for multi-relay node multi-source node pairing for selection of time slots by relay nodes that operates in a distributed fashion, with low signaling or processing overhead, and with low collision probability of signals in a common-use slot.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by advantageous embodiments of the present invention, which includes a communication system configured to convey information between source nodes and destination nodes and having relay-type transmission capability. In one embodiment, an apparatus includes an identification subsystem configured to form a source node identification list providing a number of source nodes that a relay node can support relaying information therefrom. The apparatus also includes a message generator configured to generate a first stage message in a randomly selected mini-slot in a time slot section of a plurality of sections of a common-use time slot of a communication network identifying a first source node that the relay node has capability to support when the relay node can support relaying information from one source node.

In an alternative embodiment, the identification subsystem is configured to remove a second source node supported by one of other relay nodes from the source node identification list thereof when the relay node can support relaying information from multiple source nodes. In a related, but alternative embodiment, the relay node can support relaying information from one source node in accordance with removing the second source node from the source node identification list thereof. In accordance therewith, the message generator is configured to generate a second stage message in a randomly selected mini-slot of a time slot section of the plurality of sections of the common-use time slot of the communication network identifying the first source node that the relay node has capability to support.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: FIGUREs 1 and 2 illustrate system level diagrams of a communication system including a wireless communication system that provides an environment for application of the principles of the invention;

FIGURE 3 illustrates a system level diagram of a communication element of a communication system that provides a structure for application of the principles of the invention; FIGURE 4 illustrates a system level diagram of a communication system including a wireless communication system that provides an environment for application of the principles of the invention;

FIGURE 5 illustrates a diagram of an exemplary frame structure for two consecutive frames for a communication system in accordance with the principles of the present invention; FIGURE 6 illustrates a diagram of a conventional distributed pairing scheme for a relay node-source node pairing arrangement;

FIGURE 7 illustrates a diagram of an exemplary distributed pairing method for a relay node- source node pairing arrangement constructed according to the principles of the invention; and

FIGURE 8 illustrates a comparison of pairing probability of a conventional relay node- source node-pairing scheme and a relay node-source node-pairing method according to the principles of the invention versus re lay- node number.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments are discussed in detail below.

It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to exemplary embodiments in a specific context of selection of time slots by relay nodes that operate in a distributed fashion. In general, the invention may be applied to any communication system such as a cellular or ad hoc wireless communication network [e.g., sensor networks including ad hoc wireless communication networks that are compliant under the Institute of Electronic and Electrical Engineers ("IEEE") standard 802.11 or 802.16, which is incorporated herein by reference]. The relay nodes capable of performing a relay function between a source node and a destination node in such networks send their "hello" signals sequentially. A shared-use or common-use time slot is partitioned into time slot sections that are divided into a number of mini-slot groups for the different relay nodes to send their "hello" signals.

As mentioned above, several distributed multi-relay node/single source node schemes have been previously proposed, wherein one relay node is selected among multiple relay nodes for a single source node. For example, in Bletsas, cited above, and in a paper by B. R. Hamilton, et ah, entitled "Noncooperative Routing with Cooperative Diversity," Proceedings of IEEE International Conference on Communications ICC'07, June, 2007, pp. 4237-4242, which is incorporated herein by reference, the authors propose to set a timer at each relay node.

Another approach for a distributed multi-relay node/single source node scheme is random- access based, as described by in a paper Caleb K. Lo, et al. ("Lo"), entitled "Hybrid-ARQ in Multihop Networks with Opportunistic Relay Selection," Proc. of the IEEE Intl. Conf. on Acoustics, Speech and Signal Processing, April 5, 2007, which is incorporated herein by reference. As described by Lo, after relay nodes hear a request from a single source node, the capable relay nodes will try to send their "hello" signals in a time slot. The time slot includes of a number of mini-slots. Therefore the relay nodes send their "hello" signals in a random access fashion. The pairing process is considered to be successful if at least one relay node sends out its "hello" signal without collision. Since a plurality of relay nodes compete for a limited number of mini-slots, however, the likelihood of signal collisions is significant if the number of relay nodes is large, which can be a common situation as the number of user equipment continues to grow, particularly in large metropolitan areas.

As will become more apparent, the system as described herein provides a distributed multi- relay multi-source selection scheme for source node-relay node pairing that address the limitations as set forth above. By exploiting the broadcast nature of a radio channel, a cooperative arrangement is constructed for distributed multi-source, multi-relay selection. Multi-relay, multi-source selection is combined with slot selection by employing a feedback communication path between multiple relay nodes and multiple source nodes, which effectively balances the collision risk on two stages of pairing selection and feedback transmission. In a multi-relay multi-source selection scenario, not only is pairing efficiency substantially improved, but also the signaling overhead is reduced.

Referring initially to FIGURE 1, illustrated is a system level diagram of a communication system including a wireless communication system that provides an environment for the application of the principles of the present invention. Although the communication system illustrated in FIGURE 1 represents a cellular communication system, ad hoc wireless communication systems, such as those described by IEEE standard 802.16, provide another environment for the application of the principles of the present invention. The wireless communication system may be configured to provide evolved UMTS terrestrial radio access network ("e-UTRAN") universal mobile telecommunications services. A mobile management entity ("MME")/system architecture evolution gateway ("SAE GW") (one of which is designated 110) provides control functionality for an e- UTRAN node B (designated "eNB," an "evolved node B," also referred to as a "base station," of which one is designated 120) via an Sl communication link. The base stations 120 communicate via X2 communication links. The various communication links are typically fiber, microwave, or other high-frequency metallic communication paths such as coaxial links, or combinations thereof.

The base stations 120 communicate with user equipment (one of which designated 130), which is typically a mobile transceiver carried by a user. Thus, communication links (designated "Uu" communication links) coupling the base stations 120 to the user equipment 130 are air links employing a wireless communication signal such as a 1.8 gigahertz ("GHz") orthogonal frequency division multiplex ("OFDM") signal.

Turning now to FIGURE 2, illustrated is a system level diagram of a communication system including a wireless communication system that provides an environment for the application of the principles of the present invention. The wireless communication system provides an e-UTRAN architecture including base stations (one of which is designated 210) providing e-UTRAN user plane (packet data convergence protocol/radio link control/media access control/physical) and control plane (radio resource control) protocol terminations towards user equipment 220. The base stations 210 are interconnected with X2 interfaces or communication links. The base stations 210 are also connected by S 1 interfaces or communication links to an evolved packet core ("EPC") including a mobile management entity ("MME")/system architecture evolution gateway ("SAE GW") (one of which is designated 230). The Sl interface supports a multiple entity relationship between the mobile management entity/system architecture evolution gateway 230 and the base stations 210. For applications supporting inter-public land mobile handover, inter-eNB active mode mobility is supported by the mobile management entity/system architecture evolution gateway 230 relocation via the Sl interface.

The base stations 210 may host functions such as radio resource management (e.g., internet protocol ("IP") header compression and encryption of user data streams, ciphering of user data streams, radio bearer control, radio admission control, connection mobility control, dynamic allocation of resources to user equipment in both the uplink and the downlink, selection of a mobility management entity at the user equipment 220 attachment, routing of user plane data towards the user plane entity, scheduling and transmission of paging messages (originated from the mobility management entity), scheduling and transmission of broadcast information (originated from the mobility management entity or operations and maintenance), and measurement and reporting configuration for mobility and scheduling. The mobile management entity/system architecture evolution gateway 230 may host functions such as distribution of paging messages to the base stations 210, security control, termination of U-plane packets for paging reasons, switching of U-plane for support of the user equipment 220 mobility, idle state mobility control, and system architecture evolution bearer control. The user equipment 220 receives an allocation of a group of information blocks from the base stations 210. Turning now to FIGURE 3, illustrated is a system level diagram of a communication element or device 310 of a communication system that provides a structure for application of the principles of the present invention. The communication element 310 may represent, without limitation, a base station, user equipment such as a terminal or mobile station, a network control element, communication node, or the like. The communication element 310 includes, at least, a processor 320, memory 340 that stores programs and data of a temporary or more permanent nature, an antenna 350, and a radio frequency transceiver 360 coupled to the antenna 350 and the processor 320 for bidirectional wireless communication. The communication element 310 may provide point- to-point and/or point-to-multipoint communication services.

The communication element 310, such as a base station in a cellular network, may be coupled to a communication network element 370, such as a network control element of a public switched telecommunication network ("PSTN"). The network control element 370 may, in turn, be formed with a processor, memory, and other electronic elements (not shown). The network control element 370 generally provides access to a telecommunication network such as a PSTN. Access may be provided using fiber optic, coaxial, twisted pair, microwave communication, or similar link coupled to an appropriate link-terminating element. A communication element 310 formed as a mobile station is generally a self-contained device intended to be carried by an end user. The processor 320 in the communication element 310, which may be implemented with one or a plurality of processing devices, performs functions associated with its operation including, without limitation, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the communication element, including processes related to management of resources. Exemplary functions related to management of resources include, without limitation, hardware installation, traffic management, performance data analysis, tracking of end users and equipment, configuration management, end user administration, management of user equipment, management of tariffs, subscriptions, and billing, and the like. The execution of all or portions of particular functions or processes related to management of resources may be performed in equipment separate from and/or coupled to the communication element 310, with the results of such functions or processes communicated for execution to the communication element 310. The processor 320 of the communication element 310 may be of any type suitable to the local application environment, and may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors ("DSPs"), and processors based on a multi-core processor architecture, as non-limiting examples. The transceiver 360 of the communication element 310 modulates information onto a carrier waveform for transmission by the communication element 310 via the antenna 350 to another communication element. The transceiver 360 demodulates information received via the antenna 350 for further processing by other communication elements.

The memory 340 of the communication element 310, as introduced above, may be of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. The programs stored in the memory 340 may include program instructions that, when executed by an associated processor 320, enable the communication element 310 to perform tasks as described herein. Exemplary embodiments of the system, subsystems, and modules as described herein may be implemented, at least in part, by computer software executable by processors 320 of, for instance, the user equipment and the base station, or by hardware, or by combinations thereof. As will become more apparent, systems, subsystems and modules may be embodied in the communication element 310 as illustrated and described above.

In one aspect, when the communication element 310 is a relay node as set forth herein, the relay node is configured to convey information between source nodes and a destination node in a communication network. The relay node includes an apparatus (e.g., a processor 320) with an identification ("ID") subsystem 330 configured to form a source node identification list providing a number of source nodes that the relay node can support the relay of information therefrom. The processor 320 also includes a message generator 335 configured to generate a first stage message in a randomly selected mini-slot in a first time slot section of a plurality of sections of a common-use time slot of the communication network identifying a first source node that the relay node has capability to support when the relay node can support the relay of information from one source node. The relay node also includes a transceiver 360 configured to transmit the first stage message identifying the first source node that the relay node has capability to support when the relay node can support the relay of information from one source node. If the relay node can support the relay of information from multiple source nodes, the relay node is configured to listen to other relay nodes and remove a second source node supported by one of the other relay nodes from the source node identification list thereof via the identification subsystem 330 of the processor 320. As a result, the relay node may now support the relay of information from one source node (e.g., the first source node) and subsequently the message generator 335 is configured to generate (and the transceiver 360 is configured to transmit) a second stage message in a randomly selected mini-slot of a time slot section identifying the first source node that the relay node has capability to support.

Turning now to FIGURE 4, illustrated is a system level diagram of a communication system including a wireless communication system that provides an environment for application of the principles of the invention. The wireless communication system includes a plurality of communications nodes (designated Nl ... N 12), wherein some communications nodes may be base stations and/or user equipment. A communications node (e.g., a base station N6) may directly communicate wirelessly to a communications node (e.g., user equipment N5) without requiring the assistance of a wireless intermediary such as a relay node. Alternatively, a communications node (e.g., user equipment N9) may receive transmissions from the communications node N6 through a communications node (e.g., user equipment N8) operating as a relay node. With continuing reference to FIGURE 4, dashed lines illustrate transmissions between pairs of communications nodes. For example, dashed line Ll illustrates a transmission(s) between communications node N2 and communication node N3, and dashed line L2 illustrates a transmission(s) between communications node N6 and communication node N8. The communications nodes may schedule transmissions with one another to help avoid transmission collisions. For example, communications nodes may transmit transmission reservations at specified times to inform other communications nodes of their desire to transmit, the size of transmission, the intended recipient, and so forth.

Turning now to FIGURE 5, illustrated is a diagram of an exemplary frame structure for two consecutive frames for a communication system in accordance with the principles of the present invention. More specifically, the frames comply with an IEEE standard 802.16 compliant ad hoc wireless communications network. Of course, analogous frame structures are employed in other communication systems and networks. A frame 505 in an IEEE standard 802.16 compliant ad hoc wireless communications network includes a control subframe 510 and a data subframe 520. The control subframe 510 may be used to create and maintain cohesion between different systems and to coordinate scheduling of data transfers. The control subframe 510 includes several transmit opportunities (one of which is designated 512), while the data subframe 520 includes time slot sections partitioned into a plurality of mini-slots (one of which is designated 522) that may be utilized by a communications node to transmit data. A mini-slot is a basic unit for bandwidth allocation with a transmission occupying one or more mini-slots 522. In an exemplary embodiment, each transmit opportunity 512 may embody a basic unit of transmission in accordance with the mini- slots 522 or each transmit opportunity 512 may be a time slot section as provided herein such that the transmit opportunities 512 can further be divided into multiple mini-slots 522 for a relay node to provide feedback.

The communications nodes in a wireless communication system may utilize a specified method for setting up pair- wise (or even multicast) communication links between communication nodes. Furthermore, a routing mechanism is employed for determining a route from a source node to a destination node, potentially through an intermediate relay node. A distributed solution has not been previously proposed for relay node-source node pairing. Neither the timer-based scheme cited previously hereinabove or the random-access based scheme provide effective relay node-source node pairing, because these methods will produce a likely conflict on multi-source node selection for relay node-source node pairing, so that the pairing probability of a multi-source node scheme cannot be guaranteed. Moreover, when multiple relay nodes are involved in source node -relay node pairing, the above-mentioned methods also suffer from severe collisions at the stage of multi-relay node feedback after the multi-source node selection process. For a centralized relay network, a possible solution is for all the relay nodes to evaluate their channels to all the source nodes, and send their capable-serving source node identifications to a respective central communication node (e.g., base station). Thus, the base station gets a two- dimensional matrix for possible relay node-source node pairs. The base station then properly selects the relay node-source node pairs and notifies each relay node. The centralized relay node-source node pairing scheme, however, requires high signaling/feedback overhead.

An efficient distributed pairing methodology for a relay node-source node scenario, constructed according to the principles of the invention, is now described. After the relay nodes hear relay requests of the source nodes, the relay nodes evaluate the source node -relay node and relay node-destination node channels to build up a source node identification list of source nodes that can be capably served. A common-use time slot is divided into a plurality of time slot sections of mini-slots. In each time slot section of mini-slots, only those relay nodes whose source node identification list contains one source node send out their "hello" signal, randomly in a first mini- slot. The relay nodes whose source node identification lists contain multiple source nodes continue to listen and update their source node identification list during each section of mini-slots by removing those source nodes that already have been selected.

By exploiting the broadcast nature of a radio channel, the multi-source node selection for relay node-source node pairing is linked to a random access mode for multi-relay node feedback after pairing selection. Therefore, the above two issues are both addressed in the distributed pairing method as described herein. By introducing a priority in relay node-source node pairing and multi- relay node feedback, the distributed pairing method substantially reduces collision risks on both the multi-source node selection for source node -relay node pairing and a response transmission for multi-relay node feedback in such a relay node-source node scenario. Compared with a centralized relay node-source node pairing scheme resident in a base station, the distributed scheme for relay node-source node pairing as introduced herein advantageously saves signaling overhead. Turning now to FIGURE 6, illustrated is a diagram of a conventional distributed pairing scheme for a relay node-source node pairing arrangement. As illustrated herein, a common-use time slot 601 extends over a time window 602. The common-use time slot 601 is divided into mini-slots, such as mini-slot 603 and mini-slot 604. The mini-slots are randomly selected by the relay nodes for source node pairing. Random selection of a mini-slot is indicated in FIGURE 6 by a vertical arrow in a mini-slot. For example, in mini-slot 603 a single vertical arrow indicates random selection of that mini-slot by a relay node. In mini-slot 604, random selection of this mini-slot by two relay nodes generates a conflict, indicated by the two vertical arrows therein. For a conventional scheme, any min-slot can be randomly selected by any relay node, regardless of the multiplicity of pairing selections for that relay node.

Turning now to FIGURE 7, illustrated is a diagram of an exemplary distributed pairing scheme for a relay node-source node scenario constructed according to the principles of the invention. As illustrated herein, a common-use time slot 701 (e.g., created in a base station for a relay enhanced cellular communication system or a communication node in an ad hoc wireless communications network) extends over a time window 702. The common-use time slot 701 is divided into mini-slots, such as mini-slot 703 and mini-slot 704. The relay node-source node scenario divides the mini-slots, each potentially under contention by multiple relay nodes, into a plurality of time slot sections such as time slot sections 705, 706, and 707, according to the number of source nodes that a relay node has capability to support (e.g., one relay node may support only one source node in time slot section 705, while another relay node may support two source nodes in a time slot section 706, or three, or more source nodes in time slot section 707). In each time slot section, slotted random access is used for source node feedback and multi-relay node feedback to the other relay nodes, so that the mini-slots within each time slot section can be further randomly selected by the corresponding relay nodes according to the number of source nodes it can support. In this manner, the likelihood of mini-slot conflict is substantially reduced.

In an exemplary embodiment, during each stage of mini-slot selection, only those relay nodes that can support only one source node send out their "hello" signals, while the other relay nodes that can support multiple source nodes continue to listen. Once a relay node hears that a source node has already been selected by another relay node, the relay node updates its capability- to-support source node identification list by removing the selected source node identification. Then, those relay nodes whose source node identification lists now only contain one source node randomly select one mini-slot in the second time slot section of mini-slots to send their "hello" signals. The process continues until the mini-slots expire, thereby substantially reducing conflict probability.

As an example, for the case where the number of time slot sections is three, the method operates as set forth below. During the first stage of mini-slot selection, those relay nodes that can support only one source node send their "hello" signals, which identify their respective serving source node identification. Other relay nodes that can serve multiple source nodes continue to listen. During the second stage of mini-slot selection, a portion of the relay nodes previously capable of supporting a plurality of source nodes now become capable of supporting only one source node, since they hear that some of the source nodes are already being served by other relay nodes, as reported during the first stage of mini-slot selection. Again, those relay nodes that can now support only one source node send their "hello" signals in one mini-slot in the second section of mini-slots. During the third stage of mini-slot selection, the remaining relay nodes again remove the served source node identifications from their capable-to-support list. Then, those relay nodes whose capable -to-support source node identification list is not empty randomly select one source node to send their "hello" signal, preferably in one mini-slot in the third section of mini-slots. The communication system can also allocate another time slot section for those relay nodes whose capable-to-support source node identification list is not empty to randomly select one source node to feedback in randomly selected mini-slot.

To evaluate the performance of a communication system employing the slot-selection process as described herein, the source node-relay node pairing probability between the proposed and the conventional schemes is compared. In a simulation, it was assumed that all the relay nodes can serve all the existing multi-source nodes randomly with equal probability, and the number of source nodes that can be served by the relay nodes is also random with equal probability. For comparison, a conventional scheme was chosen as a benchmark where a slotted random access method is adopted within all the mini-slots for the relay nodes to send their "hello" signals. In this benchmark arrangement, the relay node only randomly selects one source node to feed back if its source node identification list contains more than one source node. For the specific slot structure of the simulation in accordance with the principles of the present invention, the total mini-slots were uniformly divided into three or four sections when the total number of source nodes is four or three, respectively. In the benchmark case, all mini-slots can be randomly selected by any relay node to send its "hello" signal.

Turning now to FIGURE 8 illustrated is a comparison of pairing probability of a conventional relay node-source node-pairing scheme and a relay node-source node -pairing method according to the principles of the invention versus relay- node number. From FIGURE 8, it can be seen that the method constructed according to the principles of the invention (designated "Prop") advantageously achieves higher pairing probability than the conventional scheme (designated "Bench"). Also, it can be observed in FIGURE 8 that pairing probability diminishes when relay node number becomes very large. A principal reason for this diminution is transmission collision during feedback from a large number of relay nodes. When the number of source nodes is small, the reduction for the pairing probability is also less dramatic for a large number of relay nodes. Nonetheless, the pairing arrangement of the invention performs in a superior manner for a large number of relay nodes. Thus, a distributed pairing scheme for relay node-source node selection has been introduced.

A common-use time slot for relay node-source node pairing is divided into mini-slots, and each mini-slot is divided into a plurality of time slot sections, each section representing the adjusted number of source nodes that a relay node has capability to support. In each time slot section, slotted random access is used for multi-relay node feedback to other relay nodes or source nodes, so that the mini-slots within each section can be further randomly selected by the corresponding relay nodes according to the number of source nodes it can support. Those relay nodes that can support only one source node send out their "hello" signals, while other relay nodes that can support multiple source nodes continue to listen. Remaining relay nodes remove the served source node identifications from their capable-to-support list. Those relay nodes whose capable-to-support source node identification list is not empty randomly select one source node to send their "hello" signal, preferably in one mini-slot in a latter time slot section of mini-slots. The communication system can also allocate another time slot section for those relay nodes whose capable-to-support source node identification list is not empty to randomly select one source node to feedback in randomly selected mini-slot. In this manner, collision probability is substantially reduced without incurring significant processing overhead.

A wireless communication system including source node -relay node pairing with reduced collision probability and processing overhead. A common-use wireless time slot is divided into a plurality of sections according to the number of source nodes and destination nodes that a relay node can support. A relay node capable of supporting one relay communication link between a source node and an associated destination node transmits a message in a randomly selected mini-slot in a first time slot section. A relay node capable of supporting two source nodes and associated destination nodes deletes from its list of source nodes that it can support those source nodes identified in first-stage messages by other relay nodes, and transmits a correspondingly altered support message. During a later relay-node selection stage, a relay node capable of supporting multiple pairs after deleting previously announced nodes from its count transmits a message identifying its multi-source node support capability. The present invention, therefore, provides a wireless communication system (e.g., including a wireless cellular communication network) configured to convey information between source nodes and destination nodes and having relay-type transmission capability. In one embodiment, the wireless communication system includes a first relay node configured to create a source node identification list providing that the first relay node can support the relay of information from one source node. The wireless communication system also includes a second relay node configured to create a source node identification list providing that the second relay node can support the relay of information from multiple source nodes. The wireless communication system further includes a communication node (e.g., a base station) configured to allocate a common-use time slot divided into a plurality of time slot sections according to a number of the source nodes that a relay node has capability to support. The time slot sections are further divided into a plurality of mini-slots. The first relay node is configured to transmit a first stage message in a randomly selected mini-slot of a time slot section identifying the source node that the relay node has capability to support.

Additionally, the second relay node is configured to listen to the first relay node and remove the source node supported by the first relay node from the source node identification list thereof. As a result, the second relay node may now support the relay of information from one source node and subsequently is configured to transmit a second stage message in a randomly selected mini-slot of a time slot section identifying the source node that the second relay node has capability to support. Of course, the stages of operation as set forth above continue according to the number of relay nodes in the communication system. In another aspect, a relay node configured to convey information between source nodes and a destination node in a communication network includes a processor configured to form a source node identification list providing a number of source nodes that the relay node can support the relay of information therefrom. The relay node also includes a transceiver configured to transmit a first stage message in a randomly selected mini-slot in a time slot section of a plurality of sections of a common-use time slot of the communication network identifying the source node that the relay node has capability to support when the relay node can support the relay of information from one source node. If the relay node can support the relay of information from multiple source nodes, the relay node is configured to listen to other relay nodes and remove the source node supported by one of the other relay nodes from the source node identification list thereof. As a result, the relay node may now support the relay of information from one source node and subsequently is configured to transmit a second stage message in a randomly selected mini-slot of a time slot section identifying the source node that the relay node has capability to support.

As described above, the exemplary embodiment provides both a method and corresponding apparatus consisting of various modules providing functionality for performing the steps of the method. The modules may be implemented as hardware (including an integrated circuit such as an application specific integrated circuit), or may be implemented as software or firmware for execution by a computer processor. In particular, in the case of firmware or software, the exemplary embodiment can be provided as a computer program product including a computer readable storage structure embodying computer program code (i.e., software or firmware) thereon for execution by the computer processor. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. For example, many of the features and functions discussed above can be implemented in software, hardware, or firmware, or a combination thereof. Also, many of the features, functions and steps of operating the same may be reordered, omitted, etc., and still fall within the broad scope of the present invention.

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

WHAT IS CLAIMED IS:

1. An apparatus, comprising: an identification subsystem configured to form a source node identification list providing a number of source nodes that a relay node can support relaying information therefrom; and a message generator configured to generate a first stage message in a randomly selected mini-slot in a time slot section of a plurality of sections of a common-use time slot of a communication network identifying a first source node that said relay node has capability to support when said relay node can support relaying information from one source node.

2. The apparatus as recited in Claim 1 wherein said identification subsystem is configured to remove a second source node supported by one of other relay nodes from said source node identification list thereof when said relay node can support relaying information from multiple source nodes.

3. The apparatus as recited in Claim 2 wherein said relay node can support relaying information from one source node in accordance with removing said second source node from said source node identification list thereof, said message generator being configured to generate a second stage message in a randomly selected mini-slot of a time slot section of said plurality of sections of said common-use time slot of said communication network identifying said first source node that said relay node has capability to support.

4. The apparatus as recited in Claim 1 wherein said apparatus is coupled to a transceiver configured to transmit said first stage message identifying said first source node that said relay node has capability to support when said relay node can support relaying information from one source node.

5. The apparatus as recited in Claim 1 wherein said relay node and said first source node form a source node-relay node pair.

6. An apparatus, comprising: means for forming a source node identification list providing a number of source nodes that a relay node can support relaying information therefrom; and means for generating a first stage message in a randomly selected mini-slot in a time slot section of a plurality of sections of a common-use time slot of a communication network identifying a first source node that said relay node has capability to support when said relay node can support relaying information from one source node.

7. The apparatus as recited in Claim 6 wherein said means for forming includes removing a second source node supported by one of other relay nodes from said source node identification list thereof when said relay node can support relaying information from multiple source nodes.

8. The apparatus as recited in Claim 7 wherein said relay node can support relaying information from one source node in accordance with removing said second source node from said source node identification list thereof, said apparatus further comprising generating a second stage message in a randomly selected mini-slot of a time slot section of said plurality of sections of said common-use time slot of said communication network identifying said first source node that said relay node has capability to support.

9. The apparatus as recited in Claim 6 further comprising means for transmitting said first stage message identifying said first source node that said relay node has capability to support when said relay node can support relaying information from one source node.

10. The apparatus as recited in Claim 6 wherein said relay node and said first source node form a source node-relay node pair.

11. A computer program product comprising program code stored in a computer readable medium configured to form a source node identification list providing a number of source nodes that a relay node can support relaying information therefrom, and generate a first stage message in a randomly selected mini-slot in a time slot section of a plurality of sections of a common-use time slot of a communication network identifying a first source node that said relay node has capability to support when said relay node can support relaying information from one source node.

12. The computer program product as recited in Claim 11 wherein said program code stored in a computer readable medium is configured to remove a second source node supported by one of other relay nodes from said source node identification list thereof when said relay node can support relaying information from multiple source nodes.

13. The computer program product as recited in Claim 12 wherein said relay node can support relaying information from one source node in accordance with removing said second source node from said source node identification list thereof, said program code stored in a computer readable medium is configured to generate a second stage message in a randomly selected mini-slot of a time slot section of said plurality of sections of said common-use time slot of said communication network identifying said first source node that said relay node has capability to support.

14. The computer program product as recited in Claim 11 wherein said program code stored in a computer readable medium is configured to transmit said first stage message identifying said first source node that said relay node has capability to support when said relay node can support relaying information from one source node.

15. The computer program product as recited in Claim 11 wherein said relay node and said first source node form a source node-relay node pair.

16. A method, comprising: forming a source node identification list providing a number of source nodes that a relay node can support relaying information therefrom; and generating a first stage message in a randomly selected mini-slot in a time slot section of a plurality of sections of a common-use time slot of a communication network identifying a first source node that said relay node has capability to support when said relay node can support relaying information from one source node.

17. The method as recited in Claim 16 wherein said forming is configured to remove a second source node supported by one of other relay nodes from said source node identification list thereof when said relay node can support relaying information from multiple source nodes.

18. The method as recited in Claim 17 wherein said relay node can support relaying information from one source node in accordance with removing said second source node from said source node identification list thereof, said method further comprising generating a second stage message in a randomly selected mini-slot of a time slot section of said plurality of sections of said common-use time slot of said communication network identifying said first source node that said relay node has capability to support.

19. The method as recited in Claim 16 further comprising transmitting said first stage message identifying said first source node that said relay node has capability to support when said relay node can support relaying information from one source node.

20. The method as recited in Claim 16 wherein said relay node and said first source node form a source node-relay node pair.